1. Field
Exemplary embodiments of the present invention relate to a semiconductor design technology, and more particularly, to a reservoir capacitor and a semiconductor device including the same.
2. Description of the Related Art
A semiconductor device such as a dynamic random access memory (DRAM) needs to operate at a high speed with a low power. At a high speed operation of the semiconductor device, current supply is interrupted by inductance no matter how little the inductance is. When reducing power consumption, a delay of a circuit at a low power voltage is significantly affected and a malfunction of the semiconductor device may be caused by noise of the low power voltage.
To reduce the noise of a power voltage, overall impedance of the device needs to be reduced through small impedance between an external power supply and an on-chip circuit of the device or large capacitance of a reservoir capacitor disposed in a peripheral area of an internal circuit of the device. The reservoir capacitor is used in a power supply device to minimize a voltage-drop caused by power consumption.
In general, a reservoir capacitor has been developed to have a large capacitance through structure of a cell capacitor disposed in a memory cell array region. The cell capacitor is mainly used due to a large capacitance per an area of a MOS capacitor. The cell capacitor is formed in a serial cell array structure. The reservoir capacitor is used for a self noise decoupling, which reduces a power noise introduced between a power supply and a ground. In addition to the power noise between the power supply and the ground, a domain crossing noise may occur between heterogeneous power supplies. Thus, the cell capacitor is disposed between the power supplies to reduce the domain crossing noise. That is, the cell capacitors are disposed between a first power supply and a second ground and between a second power supply and a first ground.
However, in view of an area of the device a capacitor design both for the self noise decoupling and for reducing the domain crossing noise is cumbersome, therefore, a capacitor for reducing the domain crossing noise is not used often and the domain crossing noise remains.